This invention relates to a control system for use in a network, and more particularly an ISDN data and telecommunications network.
The invention relates in specific embodiments thereof to the B-ISDN user-network protocol Q.2931, as standardized by the ITU-T.
This protocol specifies the required form of each message, and a control system at a network node must be able to decode an incoming signalling message and then perform error checking. The required error checks are specified in Chapter 5.6 of the Q.2931 specification.
Thus, in accordance with the prior art, the incoming stream of bits which represents the signalling message is decoded and converted into a particular format, and error checking is then performed.
An incoming signalling message will consist of a number of different components, some of which are essential, that is they must be present for the message to be able to be processed at all, and others of which are optional, that is the message can be processed even if those elements are not present. However, in accordance with the prior art, it is necessary to decode the whole of each incoming message, before performing error checking. If one or more of the essential message components is absent or contains an error, the computational effort required to decode the remaining elements of the message will have been wasted.
In embodiments of the present invention, therefore, the message is decoded in stages. More specifically, the elements which must be present can be decoded and checked for errors before the optional elements are decoded. Then, if there is an error in one of the compulsory elements, or if such an element is missing entirely, it will not have been necessary to decode the remainder of the message.
This has the advantage that less computational effort is wasted on messages which cannot be processed.